Research and development are in progress for increasing the size of display panels including organic EL elements. An organic EL element typically includes a pair of electrodes and one or more functional layers disposed between the electrode pair. The functional layers at least include a light-emitting layer containing an organic compound. The thickness of the light-emitting layer and luminance in light emission are co-related. Due to this, it is beneficial that in a display panel, light-emitting portions (light-emitting layer portions that actually emit light) have uniform thickness. Much research is being conducted as to how light-emitting portions can be provided with uniform thickness, in the endeavor to increase the size of display panels.
Meanwhile, typical methods applied in forming light-emitting layers are classified largely into dry processes and wet processes. One example of a dry process is vacuum vapor deposition. One example of a wet process is inkjet deposition. It is commonly regarded that wet processes are suitable for manufacturing display panels of large sizes, in terms of both accuracy and cost.
A typical organic EL display panel whose manufacturing involves a wet process includes banks disposed over a substrate. The banks define areas in which light-emitting layers are formed. The banks may be arranged according to one of the two following arrangements. One type of arrangement is the so-called pixel bank structure, where banks are arranged to form a grid pattern. The grid pattern defines areas respectively corresponding to light-emitting portions. The other type of arrangement is the so-called linear bank structure, where linear banks all extending in one same direction are arranged. The linear banks define a plurality of areas respectively corresponding to lines of light-emitting portions disposed along the one direction. One example of the linear bank structure can be found disclosed in Patent Literature 1.
With the linear bank structure, a solution containing an organic compound used for light-emitting layers is capable of flowing in areas between the linear banks, in parallel to the direction in which the linear banks extend. In the following, such a solution is referred to as an ink, and further, the direction in which the linear banks extend is referred to as a column direction. Due to this flow of ink, the risk is reduced of film thickness unevenness between light-emitting portions occurring, even if not the same amount of ink is applied to all positions along the column direction.
Further, ink typically has great surface tension. Due to this, when an abnormality occurs, such as drying of the ink progressing quickly at a certain area between banks or a foreign substance existing at a certain area between banks, ink gathers towards and is accumulated where the abnormality has occurred. In particular, with the linear bank structure, ink flow along the column direction occurs as described above. As such, when an abnormality occurs, this ink flow results in ink from a vast area gathering towards and being accumulated where the abnormality has occurred. This results in film thickness unevenness occurring over a relatively great area along the column direction. This problem can be found disclosed in Patent Literatures 2, 3, and 4.
In view of this problem, Patent Literatures 2, 3, and 4 disclose suppressing the gathering and accumulation of ink as described above by providing, in each space (inter-bank space 960) between banks 95, obstacles (sub-banks 94) restricting ink flow and each disposed at an area (a non-light-emitting portion 962) between a pair of light-emitting portions 961 disposed in the inter-bank space 960. FIG. 13 illustrates an organic EL display panel 90, which is one example of a display panel with such a structure.